The present invention relates to the art of electric arc welding with a welder having a power supply of the switching type and more particularly to an electric arc welder of this type combined with a novel and unique method to design the waveforms used by the welder.
Electric arc welding involves the movement of an electrode toward a workpiece while current is passed through the electrode and across an arc between the electrode and workpiece. Although some electric arc welders utilize a non-consumable electrode, most of the mass production arc welding involves an electrode which is consumed during the welding process whereby the electrode is melted by the arc and deposited on the workpiece. Thus, an arc welding process includes variable process characteristics, such as wire speed or electrode speed, gas composition, electrode diameter and workpiece metal. The actual electrical arc welding process at the production site takes into consideration these characteristics and involves a non-linear complex control system which determines the applicable metal transfer mode and the electrical parameters of the power supply performing the welding process. In order to achieve desirable results, a waveform is selected having several control parameters, which waveform is customized for the exact condition of each welding application. Thus, controlling arc welding has become an art which demands substantial knowledge and experience to select a waveform having several control parameters to produce an optimum welding process. A large number of controllers have been developed for use with electric arc welders that have real time current waveforms developed by welding engineers to optimize the welding process performed in the field. To accomplish this objective, a microprocessor based controller has been developed and is now used that allows an operator in the field to select one of many welding waveforms by merely using one of several overlays. This successful microprocessor based controller is illustrated in Blankenship U.S. Pat. No. 5,278,390 that is incorporated by reference herein. By using a known template for the controller, an operator selects a welding waveform having the desired control parameters especially developed for the selected weld process by a skilled welding engineer. This successful controller had a certain amount of adjustability in the field; however, such on-site adjustments were limited. Mass production use of arc welders has created a demand for the ability to conveniently adjust certain control parameters of the welding waveform in the field, especially when the welding process conditions are different than what is used in designing standard waveforms shipped with the welders (such as cable length, shielding gas and welding wire). Thus, there was a need for a controller to be used with an electric arc welder, where the controller can process a desired waveform that is adjusted interactively at the manufacturing site so the waveform is optimized for welding conditions and welding requirements for the job.
To fill this need, an electric arc welder was developed with a microprocessor based controller for the specific arc welder. This welder is shown in Hsu U.S. Pat. No. 6,002,104 incorporated by reference herein. The welder has a switching type power supply for creating a welding cycle, with a real time current waveform constituting several control parameters by rapidly switching a D.C. current in a controlled fashion by a pulse width modulator and it will be described with respect to such switching type power supply. This prior patented controller was used with various switching type power supplies normally used in electric arc welders; however, the Hsu patent shows a down chopper power supply for simplicity. In practice, an inverter type power supply having a waveform controlled by a pulse width modulator was controlled in accordance with the present invention. The microprocessor based controller included means for displaying a waveform generated on an electrically operated waveform screen, such as a CRT. In this manner, the operator at the production site viewed the actual waveform to be processed by the electric arc welder under the direction of the patented controller. Interactive means were employed for manually adjusting at least a portion of the waveform displayed on the waveform screen to generate a new waveform operating on the waveform screen and having the desired control parameters. Consequently, a prebuilt waveform was first displayed on the CRT, normally in a graph exhibiting current versus time. To change one of the control parameters, such as background current, peak current, current ramp, etc., a manual adjustment of the prebuilt waveform was performed manually and interactively on the waveform screen. In this manner, a new current waveform was exhibited on the waveform CRT screen. In accordance with somewhat standard practice, before the patented arc welder the pulse width modulator of the power supply was controlled in accordance with the newly created current waveform to cause the power supply itself to generate a welding cycle with the real time waveform corresponding to the new waveform on the waveform screen. The welder power supply executed the new control parameters exhibited as control parameters in the new waveform. In this manner, a desired waveform was exhibited and used by the electric arc welder. If there was a need to change a control parameter of the exhibited waveform, the waveform itself was modified visually by the operator on site and then employed for control of the electric arc welder. This interactive changing of the waveform, as it was visually displayed on a waveform screen, was novel to the welding field and was implemented by including a JAVA virtual machine with a welder control application program or an applet running within a browser in JAVA language. The JAVA control program was dedicated to the specific electric arc welder combined with the controller. Thus, the consumer product was an electric arc welder having a power supply with a microprocessor based controller that was driven by a program in JAVA language. This concept was accomplished by using a JAVA virtual machine as part of the on site controller. This new electric arc welding was interactively manipulated to create a waveform for controlling the actual real time waveform of the welding process. The controller performed its functions through real time adjustment of the pulse width modulator used in the switching power supply driving the welder.
In a welder using the patented technology of Hsu U.S. Pat. No. 6,002,104 the welder has a microprocessor with a JAVA virtual machine and controlled by at least one control application program in JAVA language. The program was dedicated to the particular welder being controlled. The microprocessor system included hardware with a first interface for an interactive display screen and a second interface for a manual data entry device, such as mouse or keyboard, that was used interactively to change the waveform on the display screen preparatory to the waveform being implemented on a digital communication link (such as ethernet or infrared) for outputting control parameters to the welder. The same communication channel was used to input operating parameters from the welder. In this manner, the electric welder was controlled by manual manipulation of the actual waveform to be used in the welding process preparatory to implementation of the welding process. As changes are required, certain control parameters were adjusted on the display screen to merely change the shape of the waveform being displayed. When the operating parameters from the welder were inputted to the microprocessor of the controller, a separate xe2x80x9cscopexe2x80x9d application program in JAVA language was selected and implemented by the controller. In this manner, the CRT of the controller was converted from a waveform editor to an oscilloscope display for reading parameters from the welder and for displaying these parameters as a soft oscilloscope on the face of the controller. The scope display used a window separate and distinct from the window used for editing the waveform. The screen of the controller was used to display either the waveform processed by the waveform editor application program or the oscilloscope plots processed by the scope application program. Both programs were processed by the JAVA virtual machine which was a part of the welder. The application programs were loaded into the virtual machine by a CD ROM that is loaded at the factory to program each of the welders preparatory to delivery. The physical media of distributing the JAVA object code or bytecode from the welding manufacturer to the customer used other forms, such as a floppy diskette, E-mail, web page and down loading by a modem. To change the operation program for the welders in the field, the patented welder periodically updated the control application program and/or the scope application program of the welders by a new CD ROM or by an Internet feed.
The patented controller of Hsu U.S. Pat. No. 6,002,104 displayed on its screen a waveform series of read out devices adjacent the waveform screen. A series of control parameters for the waveform were displayed adjacent the waveform screen, as read out values. The waveform was displayed on the waveform screen and contained a series of control parameters, some of which were recorded as read out values on the face of the controller adjacent the waveform screen. This total display is shown in FIG. 2 and is referred to as the graphic user interface or GUI. This display is used interactively to modify the waveform. The variable tables and waveform logic is provided by the memory stack as shown in FIG. 4. As an example of the display usage, the peak current of the waveform is displayed in an alpha numerical numbers on the face of the controller. As the waveform was modified interactively on the screen, the read out value was automatically changed accordingly. In addition, by adjusting one or more of the displayed control parameters at the read out device, the waveform itself was changed accordingly. The displayed control parameters, shown in the read out devices, had corresponding lock control parameter means for manually locking the display control parameters at preselected read out values. In this manner, the waveform was adjusted to change the value of a locked out control parameter. The prior art controller included a first override that was implemented to limit the value of one or more of the control parameters. In other words, if maximum current of the welder was at a set point, the control program processing a given waveform would prevent adjustment, either interactively or by a read out device, of the current to a level above the set maximum level. The same concept was used with a relational constraint wherein there is a fixed relationship of one control parameter to another control parameter. This fixed relationship was maintained. In this fashion, when one of the control parameters was adjusted, the other parameter is adjusted accordingly to maintain the set, fixed relationship. These are schemes utilized in the prior art patented welder to constrain the interactive manipulation of the waveform on the waveform screen or adjustment of the waveform through read out devices on the face of the controller. The JAVA virtual machine of the prior controller is provided with two or more application programs that are stand alone and can be selected by the operator who selects one or the other programs to be executed. The hardware of the controller includes a mouse or keyboard which latches onto certain points on the displayed waveform and allows the points to be moved or dragged in accordance with standard microprocessor operation. Consequently, there were graphically manipulating current waveforms for an arc welder in real time using JAVA technology. The welder monitors the actual waveform of the welder by analyzing operating parameters and using measurable electrical signals, such as arc current and voltage, derivative signals, such as impedance, power and energy, and process modes of operation. By using this concept, the operating signals or parameters from the welder itself were used to display and apply impedance of the arc and cable and instantaneous power of the arc and cable. Average current and voltage are sampled at a fixed rate and the welding time and the accumulated energy were also capable of being displayed in real time. If the optional scope program was employed, the output waveform created on the screen was analyzed and numerical data was displayed from various aspects of the displayed operating parameters. Other aspects of the actual operating condition of the welder were displayed and analyzed by using the scope program of the controller, not forming a part of the present invention.
In the prior art electric arc welder patented in Hsu U.S. Pat. No. 6,002,104, the processing logic was fixed and inflexible so that only certain types of waveforms pre-built into the program could be processed. For instance, a fixed wave shape template was selected for display and manipulation. See FIG. 3. The basic aspects of the template were fixed logic. Thus, the welder with a JAVA virtual machine could only select fixed templates for processing of specific current waveforms. There was no ability to select from a memory location certain data and display this as a waveform in a manner to change the behavior of the waveform template. In the prior art unit, the weld program compiled as object code or bytecodes was fixed to manipulate a fixed waveform logic of FIG. 4. If the waveform in FIG. 4 is changed, the JAVA source code must be changed to support the new waveform logic.
The present invention involves designing the various waveforms for the work point stack to output selected waveforms for controlling the electric arc welder through a waveform generator in accordance with standard technology.
In accordance with the invention, there is provided a method of designing the series of waveforms for current cycles generated by a waveform generator that controls the individual waveforms of an electric arc welder. A welding engineer designs the various waveforms for the work points such as wire feed speed values. They are then loaded into a memory stack for use by the waveform generator when the welder is to be operated at the various work points. When designing the waveforms, the welding engineer utilizes perceived parameters for the waveforms. In some instances, these parameters do not produce the desired waveforms for each of the different work point operations. The present invention involves a method for designing the waveforms so that they do indeed conform to a desired implementation of the welding process. In practice, such waveforms are digitized and are stored in a memory stack by individual work points. When a give work point is selected for the weld process, that particular waveform in digitized data form is outputted for use by the waveform generator of the welder. The present invention assures consistency between the many waveforms in the stored memory stack. This method involves integrating the arc current of the waveform that has been designed for each of the many work points. In this manner, an integrated amount is obtained for each waveform stored for use at each work point. The invention involves plotting the integrated amounts for each of the work points and creating a regressive curve statistically matching the plotted amounts to reveal any outlier amounts. In other words, when plotting the integrated amount for each of the work points on a graph, the graph is statistically analyzed by a computer program using a regression, either linear or polynomial, to provide a curve. This curve reveals any outlier which is a deviation of the integrated amount from the line which statistically defines the proper value for the various integrated amounts. Then, any of the outlier amounts that deviate from the regression curve are noted so the particular waveform that is deviated from the statistical curve is manually changed in accordance with standard practice using previous technology incorporated by reference herein. That waveform then is redesigned and adjusted to bring the integrated amount into general conformity with the statistical regression line so that there is a smooth distribution of the integrated amounts along the regression line. In the preferred embodiment, the regression curve is a polynomial regression line. However, a linear regression line using the least squares fit concept has also been employed in practicing the invention. Either a regression line or regression curve is obtained by a standard computer algorithm for analyzing plotted values. In the preferred embodiment, the line is straight.
In accordance with another aspect of the present invention, the integrated values of the current for each waveform of the individual work points is averaged by dividing the integrated amount by the period of the waveform. This provides an average current for the individual waveforms making up the various waveforms of the work points to be used by the welder for performing a given welding process. These average values are plotted statistically to discern outliers and correct the waveforms for bring the outliers closer to the statistically developed curve. This further aspect of the invention may also employ the concept of adding a constant to the average value and then square this summation to produce points that are plotted and compared with a regression curve. This manipulation is also effected to obtain a set of waveforms in a memory stack for a given welding process that changes according to the work point selected for the process.
The invention is directed to a method whereby a value for the waveform of each waveform in a series for a given welding process is obtained, plotted and compared to a statistical curve. Deviations from this statistical curve are noted and used by the welding engineer to modify the waveform corresponding to the deviated value or amount. In this manner, the various amounts or values for the various waveforms to be used at different work points are optimized and customized.
The primary object of the present invention is the provision of a method for analyzing an amount or value of a given waveform in a series of waveforms corresponding to work points of a given process to be performed by an electric arc welder and then statistically comparing a plot of these values or amounts to identify waveforms which need to be changed and/or customized to produce smooth operation of the welder performing the welding process.
Still a further object of the present invention is the provision of a method, as defined above, which method utilizes the integrated current of each of the waveforms in the array of waveforms for the various work points.
Another object of the present invention is the provision of a method, as defined above, which method involves dividing the integrated current for each waveform by the waveform period to produce a value representing the average current. This average current is then plotted or is used to produce a calculated value by adding a constant and squaring the summation.
Still a further object of the present invention is the provision of a method, as defined above, which method allows a welding engineer to produce the desired waveforms for the various work points in a welding process and then check the waveforms to determine their deviation from desired values for subsequent customization and correction.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.